Drilling muds



Dec.

Filed Oct. 28, 1954 7 R. J. TAILLEUR 2,773,030

DRILLING MUDS 2 Sheets-Sheet 1 h ELL A/0 2.

INVENTOR.

DRILLING MUDS' Rodolfo J. Tailleur, San Tome, Venezuela, assignor to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Application October 28,1954, Serial No. 465,417 38 Claims. 01. 252'8.5)

This invention relates to improvements in drilling mud compositions of the type used in Well drilling, and more particularly it pertains to oil-in-water emulsion drilling muds having improved lubricating properties.

A substantial portion of the total time consumed during well drilling operations is taken up in the replacement of drill bits. Inasmuch as changing a bit necessitates pulling the entire string of drill stem, substituting a new bit, and rerunning the entire string of drill stem back into the borehole, it is evident that'the time consumed in making bit changes increases roughly in proportion to the depth being drilled. As wells are being drilled to ever increasing depths, the economic losses attendant upon the increasing amount of time lost in making bit changes cannot be ignored. In addition to the loss of time involved in making bit changes, the necessity for making frequent bit changes, particularly when drilling at substantial depths, may create hazards, such as increasing the likelihood of cave-ins, which may arise as a result of stopping the circulation of the drilling mud during the change of bits.

Obviously, the necessity for making a bit change is dictated by the exhaustion of the useful life of the bit. Although much has been done toward improving drill bits and drilling techniques in order to'prolong useful life,

in the present state of rotary bit development, the most frequent limiting factor of bit life is-failure of the bearings, rather than the cutting teeth.-

Thus, perhaps the most important factor tending to shorten the useful life of a drill bit'is the lack of adequate lubrication of the bearings; In the past, efforts have been made to afford lubrication for the bearings by incorporating self-contained lubricating units in the bits, That such efforts have not been entirely successful is borne out by the fact that conventional bits currently in use are not provided with such self-lubricating units. Consequently, conventional bits receive only such lubrication as may be obtained from the drilling mud being circulated therethrough. Since the bearings of the bit are subjected'to high loads, the value of conventional drilling muds as bit lubricants leaves much to be desired.

Although lubricating properties have commonly been attributed to conventional oil-in-Water emulsion drilling muds, as far as I am aware, it has not been satisfactorily demonstrated that such muds actually behave as lubricants for the bearings of drill bits under actual field conditions which impose high specific loads on the bearings of the bit. I have investigated some commonly used oilin-water emulsion drilling muds to which lubricating properties have been attributed, and on the basis of field tests and tests made with the Timken Wear and Lubricant Tester, as will be more fully described hereinafter, I have found that the lubricating properties of such muds are of no' significance with respectto the specific loads on the bearings under theconditions to which a drill bit is subjected in the'field. In other words, under such conditions, such muds have practically no lubricating value for the bearings of drill bits. i

'ice

' I have now discovered that oil-in-water emulsion drilling muds can be made to possess elfective lubricating properties and thus prolong the life of drill bits while retaining the normally desirable properties of such muds.

In accordance with my invention, I provide a drilling mud which is an emulsion of oil-in-water containing clay solids, and a Water-insoluble, oil-soluble sulfurized organic compound in the oil phase, said'sulfurized compound being present in an amount suflicient to increase the Timken load-carrying capacity of the mud to at least about 30 pounds. Such drilling muds possess excellent lubricating qualities and prolong the life of the bearings of drill bits,

. thereby'reducing the frequency of bit changes and decreasing the time diverted from actual drilling operations. The water-insoluble, oil-soluble sulfurized organic compounds utilized in the muds of my invention include such materials as sulfurized unsaturated higher fatty acids and their esters, sulfurized open-chain olefins' and polymers thereof, sulfurized higher molecular weight paraffinic hydrocarbons, sulfurizedcrude petroleum and residual fractions thereof, sulfurized terpenes, and sulfurized phenols and salts thereof. 1 i

The sulfurized unsaturated higher fatty acids are generally of 12 or more carbon atoms and include such matenials as sulfurized dodecenoic, tetrad'ecenoic, hexadec- The unsaturated fatty,

enoic, octadecenoic, etc. acids. acids obtained from'the splitting of fatty glycerides, e. g., oleic, ricinoleic, linoleic, etc. acids, form a preferred source of this class of materials. 7 or relatively pure acids, e. g., oleic acid, can be sulfurized to form the sulfurized organic compound utilized in the muds of this invention. Another good source of un-, saturated fatty acids is tall oil which. contains approximately 50 to 56 percent of .fatty acids, mainly olelc acid, 38 to 42 percent of rosin acids and 6.to 8 percent of unsapomfiable material. Since the unsaturated higher fatty acids will usually be obtained fromnatural sources,'they will normally contain no more than 18 carbon atoms.

The sulfurized unsaturated higher fatty acid esters are obta ned by the sulfurization of an ester of the fatty 'acids described above. A common source of such esters coniprises the fatty glycerides, e. g., corn oil, linseed oil, soya o l, castor O11, rape oil, cottonseed oil, tung oil, perilla Oll, menhaden oil, lard oil, etc. The esters need not be glycerides, since esters of monohydric alcoholsand the higher'unsaturated fatty acids can also be sulfurized and V successfully employed in the muds of my invention." Such" monohydric alcohol esters include sperm oil, methyl oleate, ethyl oleate, oleyloleate, as well as similaresters obtainable by alcoholysis of fatty glycerides with a mono- 4 drocarbon fraction to yield heptenes, can also be sulfurized and employed in the mudsiof the invention. Preferred materials of this class are sulfurized diisobutylene'and sulfurizedheptene.

Other hydrocarbon materials which'canfbe sulfurized to yield suitablesulfurized organic compounds include higherparafiinic hydrocarbons, such as essentially paraffinic lubricating oils and paraflinv'vax; crudexpetroleum and the various residual fractions thereof, such as topped crudes, reduced crudes, residual fuel oils and the solvent extract fractions of residual petroleum oils; and the terpenes, such as pine oil, pinene (turpentiiie) and di pentene.-

Either the'crude acids properties of the muds is ordinarily obtained. 7

fore prefer toernploy an amountof sulfurized organic compound sufiicient to provide from aboutl to 4 percent Sulfurized phenols, particularly the alkyl phenol sulfides containing at least 4 carbon atoms in one or more alkyl groups, are also useful as the sulfurized organic compounds in the muds of my invention. Such bisphenol sulfides include, fo'r example, the sec butyl and tert-fb'utyl phenol, isoamyl phenol, isooctyl phenol, nonyl phenol, triisobutyl phenol and wax alkyl phenol sulfides. Metal salts of such sulfurized phenols are also suitable, for example, the sodium, calcium, barium, zinc-and tin salts.

'The above sulfurized organic compounds can be prepared in any conventional manner known to the art such as by sulfurization with elemental sulfur, with sulfur halides, and with phosphorus sulfides. In general, I prefer to employ elemental sulfur as the sulfurizing agent because it is cheap and produces excellent sulfurized or -v ganic compounds for the purposes of this invention. Thus,

for the preparation of sulfurized organic compounds from I cating oils can be similarly treated, they can also be reacted with a phosphorus sulfide, for example, P285, P483, etc. to obtain suitable compounds. In the preparation of, sulfurized compounds from the phenols, reaction with a sulfur halide, for example, 82012, is preferred. From the foregoing description, it will be apparent that v the sulfurized organic compounds and their methods of preparation are themselves known in the art.

To obtain the desired increase in lubricating properties of-the drilling muds of this invention, the sulfurized organic compounds are incorporated into the drilling muds in amounts sufficient to increase the Timken load-carrying capacity of the mud to at'least about 30 pounds. Generally speaking, an amount of sulfurized organic com- 7 pound is employed which is sufficient to provide at least 7 about 0.5 percent of sulfur by weight, based on the oil phase of the oil-in-water emulsion drilling mud. Al'- though larger amounts of the sulfurized organic compounds can be employed, for example, amounts suflicient toprovide 8 percent or more of sulfur by weight of the oil phase, it is usually unnecessary to employ such large amounts since no further improvement in lubricating I thereof sulfur by weight of the oil phase, since experience has indicated that such amounts of sulfurized organic compound will generally result in the desired improvement in lubricating properties. It will be understood by those skilled in the art that, since the sulfur content of individual sulfurized organic compounds will vary, say from about 6 percent by weight in thecase of sulfurized Kuwait crude oil, 10 percent by weight in the case of sulfurized oleic acid to about 40 to 50 percent by weight in the case of sulfurized heptene or sulfurized diisobutylene, the exact amount of a specific sulfurized organic compound to employ will vary, depending on its sulfur content. It is obviously desirable to employ a sulfurized organic compound containing large'amounts of sulfur, since smaller amounts of such compounds can be employed to .yield the desired sulfurcontent on thefoil phase. For this reason, andfor the further reason that laboratory and field tests haveshown their superiority in conferring lubri-,

eating properties on the muds of this invention, I prefer to use the sulfurized olefins, such as sulfurized heptene and sulfurized diisobutylene.

Any clay can be utilized in the drilling muds-of this 4 invention which is commonly employed for this purpose in the art. Such clays, which form dispersions or gels with waterycan be native products, such as may be available at the well site, or a relatively pure clay, such as bentonite, or base-exchanged clays, such as lime-treated clays, etc. In general, when using clays such as bentonite,

the 'clay is employed in an amount of frorn'about 2 to 8 percent by weight of the entire composition, more or-less,

depending upon the yield (barrels of mud of 15 centipoise viscosity per ton of clay) of the clay. When native clays are employed, larger amounts, say as high as 40 percent by weight of the mud composition, can be used because they wield less barrels of mud per ton of clay.

It is characteristic of the drilling muds of this invention that they are sensitive to the presenceiof alkali metal hydroxides. By this I mean that the addition of substantial quantities of alkali metal hydroxide to these muds,

results in a loss of the lubricating properties otherwise obtained through the use of the water-insoluble, oil-.-

solublesulfurized organic compounds. similarly a -drilling mud which has already been treated withs ub stantial amounts of alkali metal hydroxide does not respond beneficially to later treatment with the sulfurized organic compound. In other words, notwithstanding thefact that oil-in-water emulsion drilling muds contain a water-insoluble, oil-soluble sulfurized organic compound, such muds will not have enhanced lubricating properties in the presence of alkali metal hydroxide. This phenomenon is unexpected and cannot be satisfactorily explained at present, particularly since the lubricating properties of the muds of this invention are not detrirnentally afiected by admixture with such materials as calcium hydroxide.

or sodium chloride.

The sensitivity of the drilling muds to, alkali metal hy-I droxide imposes certain precautions in'the use of clay defiocculants to reduce the viscosity and fiuid loss of the muds. For example, oneof the most-widely used clay defiocculants is quebracho which is generally employed with caustic soda. If the drilling muds of this invention are treated in the usual manner with the conventional quebracho-caustie soda mixture, there results a loss of the enhanced lubricating properties, although the-otherwise normal properties of the muds are retained. It is to be noted, however, that the muds of the invention will their load-carrying capacities.

cordance with this invention, containing pure bentonite as the clay in an amount of 6 percent by weight ofv the V entire mud and having a relatively high tolerance to alkali metal hydroxides, I have found that the use of 0.5 pound of caustic soda per barrel of drilling mud, although reducing the load-carrying capacity considerably, does not render the mud worthless from a lubricating stand point. However, when the caustic soda is increased to 1.0 7

pound per barrel of the mud, the lubricating properties of the mud are substantially eliminated. With other clays, or lesser amounts of clay, the caustic soda tolerance is substantially less. A

From the foregoing, it will-be apparent to those skilled in the art that no substantial amount of caustic soda should be added to the muds ofthis invention; in no event should suchamount be sufficient .to destroy the Since'in 1 enhanced lubricating properties .of' the muds. normal field practice, the amounts of caustic soda usually of the invention,'when it becomes desirable to useari alkaline treating agent with or without a clay deflocculant,"

it is preferred to employ suchalkaline materials'as, ammonia, amines; such as mono-,'di-andtri-ethanolamine,

etc. which do not have any deleterious effect on the lubria eating properties of the muds. In treating the muds of my invention with quebracho, it is possible to use this material alone, that is, without the conjoint use of caustic soda, although in such case more of the quebracho will usually be required to obtain the desired deflocculating effect.

In another aspect of my invention, I have found that the lubricating properties of my drilling muds containing the sulfurized organic compounds, as above described, are unexpectedly additionally enhanced by the use therewith of an asphalt. For example, there can be employed such materials as natural asphalts, petroleum asphalts, blown asphalts, sulfurized asphalts, the solid petroleum residues or pitches obtained in the vacuum reduction of crude oils, asphalt extract fractions obtained in the solvent refining of residual petroleum oil fractions, and the asphaltites, such as gilsonite, manjak or glance pitch, and grahamite. These asphalts range from highly viscous liquids to essentially solid materials and when present are employed in amounts of from about 5 to 75 percent by weight of the total oil phase in the oil-in-water emulsion, depending on the type of asphalt employed and its solubility or dispersibility in the oil of the oil phase. Ordinarily, from to 35 percent by weight is satisfactory. In some instances, I have found that the oil used to prepare the oil-in-water emulsion drilling muds of this invention is deficient in solvent or dispersing power for the asphalt. In such instances, it is desirable to use an auxiliary solvent or blending agent with the asphalt to insure solution or dispersion thereof in the oil phase prior to preparation of the emulsion itself. When highly aromatic petroleum distillates or the liquid extracts obtained in the solvent refining of lubricating oils are employed in the oil phase, they generally possess suflicient solvent or dispersing power for the asphalt. However, where the oil has a lower solvent or dispersing power, as where a relatively parafiinic diesel oil or fuel oil fraction is employed, such materials as liquid chlorinated diphenyl or the abovementioned liquid extracts from the solvent refining of lubricating oils can be employed as auxiliary solvents or blending agents to obtain the desired uniform dispersion or solution of the asphalt. It is also possible to cut back or thin the asphalts with a suitable solvent, e. g., a light gas oil fraction, and the thinned material can then serve as the oil phase, the amounts of asphalt falling within the proportions stated above. Incorporation of the asphalts in the oil phase can be facilitated by initially melting or finely dividing the material prior to adding the oil; blendnig can also be facilitated by heating the oil mixture to about 180 F.

The reason for the additional increase in lubricating properties of oil-in-water emulsion drilling muds containing both an asphalt and a water-insoluble, oil-soluble sulfurized organic compound is not fully understood. Nevertheless, the enhanced lubricating properties obtained by the conjoint use of these materials is so pronounced that I prefer to use both of them. Furthermore, the use of asphalt permits of the use of less sulfurized organic compound to obtain the desired lubricating properties in the muds of the invention. V

The oil employed in forming my oil-in-water emulsion drilling muds can be obtained from any suitable source. For example, crude petroleum and various petroleum fractions such as topped crudes, reduced crudes, gas oils,

kerosene, diesel fuel oils, lubricating oil fractions, the

liquid extract fractions obtained in the solvent refining of lubricating oils and mixture of these materials can be employed in the oil phase. The total oil phase of the drilling muds of the invention ranges from about 2 to 40 percent by volume of the entire drilling mud, preferably from about 5 to 25 percent. The total oil phase comprises the above-described oils, the sulfurized organic compound and an asphalt, if the latter is employed. When an emulsifying agent is also present, it is considered to be part :of the oil phase for the purpose of determiningtheamount of total oil phase in the mud.

Since the drilling muds of my invention are oil-inwater emulsion drilling muds, an emulsifying agent will normally be added during preparation of the muds to facilitate emulsification or dispersion of the oil phase in the water phase and to stabilize the emulsion obtained. Numerous emulsifying agents for preparing oil-in-water emulsions are known in the art and any of such conventional emulsifying agents can be employed for the above purposes. Depending upon the nature of the oil employed in the oil phase, it is sometimes unnecessary to employ an emulsifying agent. Thus when a crude petroleum or other residual petroleum oil, for example, a reduced crude, is employed in the oil phase, satisfactory emulsions can usually be obtained without using an emulsifying agent, since such oils ordinarily contain natural emulsifiers. However, in the use under drilling conditions of oil-in-water emulsion drilling muds, it is desirable that the mud filtrate have a low surface tension, say on the order of 40 dynes per centimeter or below. Since emulsifying agents are surface-active compounds, they will also act to reduce the surface tension of the filtrate, although not all emulsifying agents are of equal effect for this purpose. In a preferred embodiment of my invention, my drilling muds therefore contain an emulsifying agent which not only serves to assist in the emulsification of the oil and to stabilize the emulsions formed, but substantially to reduce the surface tension of the filtrate as well. I have found that emulsifying agents which are particularly suitable for the latter purpose include preferentially oil-soluble alkylaryl sulfonic acids, e. g. -wax" benezene sulfonic acids and mahogany acids, and metal salts thereof, e. g., the alkali metal, ammonium and alkaline earth metal, including calcium and magnesium, salts. Other suitable emulsifying agents include the sodium soaps of tall oil and the fatty acid esters of the anhydroalkitols, for example, sorbitan, mono-, di-, tri-oleate, sorbitan mono-stearate, etc. Of the above emulsifying agents, I prefer to employ the sodium salt of mahogany acids, because not only is it more eflective in achieving the desired reduction in surface tension of the filtrate, but it can be used in smaller amounts for this purpose than other emulsifying agents. Substantial economies'can therefore be achieved.

In; general, satisfactory results with respect to reducing the surface tension of the filtrate and stabilizing the emulsion can be obtained by the use of from about 1 to 4 pounds of emulsifying agent per barrel of the entire drill mud composition, 'sufiicient to reduce the surface tension of the filtrate substantially below that of water and preferably to about 40 dynes per centimeter or less. However, when using the preferred emulsifying agent, namely, the sodium salt of mahogany acids, it is highly advantageous to employ not more than about '2 pounds per barrel in order to avoid excessive oil'loss in the filtrate, as fully set forth in my copending application Serial No. 350,460, filed April 22, 1953, now U. S. Patent No. 2,713,032;

'In the actual practice of my invention, it is permissible to conduct the entire drilling operation with the drilling muds above described. However, initial drilling 'operations can be started with a conventional straight water- J base mud because the soft formations and the absence of high specificloads on the drill bit at the shallower depths do not require greater lubricating properties than can i be obtained with a water-base mud. Thereafter, as dictated by the requirements of drilling and the formations encountered, the water-base mud is converted to the mud of my invention. This conversion can readily be accomplished during circulation of the water-base drilling V V U. S. gallons).

amount dependent upon the total amount of the arming mud already in the system and preferably at a rate dependent upon the rate of drilling mud circulation, so as to effect a substantially uniform dispersion of the oil materials as an oil phase throughout the drilling mud system. Conventional methods can be employed for whatever mechanical agitation is necessary to achieve the proper mixing. When an emulsifying agent is employed, it is highly desirable to add the emulsifying agent to the water-base drilling mud in admixture with the oil, but if added separately, it is advisable that it be added after the oil has been added or simultaneously with the addition of the oil. If the emulsifying agent is added prior to addition of the oil phase, there is a tendency for the mud to foam excessively and this entails the risk of a blowout.

In the practice of my invention, it is also possible to convert an existing conventional oil-in-wat'er emulsion drilling mud to a drilling mud in accordance with my invention. This is also accomplished during circulation of a the drilling mud in the well by adding thereto, with agita tion with the drilling mud in the usual mud pit, a waterinsoluble, oil-soluble sulfurized organic compound or a concentrate thereof in oil. If it is desired that the converted drilling mud also contain an asphalt, the asphalt is included as an oil concentrate in solution or uniform dispersion, a blending agent and/or heating being used if required. Such concentrates can also contain an emulsifying agent and should preferably include such an agent if an asphalt is employed. The total amount of oil concentrate and the concentration of the components of the resulting drilling mud composition being prepared, taking into account the composition of the conventional oilin-water emulsion drilling 'mud being converted, will result in an oil-in-water emulsion drilling .mud having the composition of the muds of my invention, as set forth in detail above.

It will be understood that the drilling muds of my invention which have become depleted in one or more components during use, e. g., the sulfurized organic compound or emulsifying agent, can be treated with the depleted components or oil concentrates thereof to restore the desired concentration of such components.

As an example of the preparation and use of one of the preferred embodiments of my invention in drilling a well, about the first two thousand feet of hole are drilled using as the drilling mud the mud formed from water and the natural clays incorporated therein from the formations during the drilling. In case such formations are deficient in natural clays, it is permissible to add a small quantity of bentonite to the drilling mud to increase the viscosity and thixotropic and wall building properties thereof. 'Up to this point, the procedure is identical with normal drilling operations where straight water-base drilling muds are employed. At this stage,-the water-base drilling mud in the system totals about 500 barrels (barrel throughout the specificationrand claims is 42 standard It having been determined that'conversion to an oil-in-water emulsion drilling mud is now des'irable, an oil phase is prepared as follows. Into a suitable mixing vessel, there is placed 30 barrels of a diesel fuel oil and barrels of sulfurized diisobutylene having a sulfur content of about 40 percent by weight and the mixture is stirred. Thereafter, there are stirred in 4 barrels of an oil concentrate of the sodium salts of mahogany acids (the concentrate being available commercially as Petronate HL, containing about 60 percent by weight of the salts dissolved in a lubricating oil). To this mixture there is added 3500 pounds of a granulated petroleum asphalt having a melting point of about 325 to 335 F. and a penetration of 2 to 3 at 115 F. (100 gm., 5 sec.) and the mass is stirred until all of the components are uniformly blended. The oily composition thus prepared, which is to constitute the oil phase of the drilling mud, amounts to about 50 barrels and is a moderately viscous, black liquid that can be pumped readily at ordinary tern '8 peratures and emulsifies readily in the mud to form an oil in-water emulsion. The oily composition is then added to the straight water-base drilling mud by circulating the mud through the well while pouring the oilycomposition into the mud ditch through which drilling mud returns to the mud pits from the well and agitating the pits with mud guns. Drilling need not be discontinued during the change from a water-base mud to the oil-in-water'emul sion mud of my invention. After all of the oily composi tion has been added to the preexisting drillingrnud and after the mixture has been circulated through the well about two or three times, the entire drilling mud in the system is a uniform oil-in-water emulsion rnud of my in? vention. Continued drilling with the new mud results in the benefits and advantages heretofore described.

in the following illustrative examples, there are set forth certain specific embodiments of the drilling mud compositions of my invention. it, will be understood that these specific embodiments are given by way of illustration only and are not intended to limit the invention. It will be noted that, in determining the improvement in lubricating properties of the drilling muds, I have employed the well-known Timken wear and lubricant tester.- This machine is employed in the lubricating oil art to determine the load-carrying capacity of lubricants. it was obviously impractical to test the lubricating properties of all the drilling muds set forth in each of the specific examples in an actual well drilling operation,

but as is shown in Example 1, below, I have found that.

the load-carrying capacities of drilling muds, as determined by the Timken machine, are a measure of the prolongation of bit life and. other advantages obtained through the use of my drilling muds in actual drilling operations in the field. Since the load-carrying capacities of drilling funds as obtained by the Timken machine correlate well with actual field tests, it is thus possible to test the efficacy of drilling muds in the laboratory to de-' termine their suitability for use in the field.

It is characteristic of the drilling muds of this invention that they have load-carrying capacities, as'measured by the Timken machine, of not less than 30 pounds, as

compared to load-carrying capacities of 15 pounds and below for conventional oil-in-water emulsion drilling muds which have substantially no lubricating properties.

EXAMPLE 1 A well, hereinafter designated as well Nol l, was drilled 'with 3-cone roller bits and with an oil-in-water' emulsion drilling mud having the following approximate composition: Water -60% by volume. Eastern Venezuelan crude oil 15-20% by volume. Clays and other solids 10-20% by volume. Petronate 2 lbs. per barrel.

A sample of this drilling mud was tested with the Timken machine and found to have a load-carrying capacity of less than 15 pounds. a

While drilling well No. 1 between the depths of 8320 to 9198 feet and while maintaining the composition of the drilling mud substantially constant, data were collected (l) as to the number of actual hours drilled with each bit before bearing wear necessitated a change of straight water-base drilling mud which was subsequently converted to a drilling mud of this invention by the procedure specifically described hereinabove, employing as the oil phase a uniformly blended oily mixture of diesel fuel oil, granulated petroleum asphalt having a melting point of about 325 to 335 F. and a penetration of 2 to 3 at 115 F., sulfurized diisobutylene having a sulfur content of about 40 percent by weight, and Petronate. The resulting oil-in-water emulsion drilling mud had the following approximate composition: 7

Water 70% by volume. Oil 12% by volume. Clays and other solids 15% by volume. Asphalt 2% by volume. Sulfurized diisobutylene 1% by volume. Petronate 2 lbs. per barrel.

This emulsion drilling mud was tested with the Timken machine and was found to have a load-carrying capacity of 60 pounds.

vention, the bits in well No. 2 were kept in the drilling cycle at the bottom of the hole after the cutting teeth had been worn past the point where they would .normally have been replaced. Bits are normally replaced as the cutting teeth become worn because of the danger of failure of the bearings of the bit with continued use, and the ensuing possibility of a fishing job to recover the cones of the bit. If in the test well employing the mud of my invention, the bits had been changed when the cutting teeth were Worn, in accordance with normal practice, the number of feet of hole made per hour of total drilling rig time would have shown a substantial increase.

It was also found in testing the mud of my invention in well No. 2 that, although the cutting teeth of the bits had been substantially worn out, in no case was a hearing failure experienced, as would have been the case if the cutting teeth of the bits used in well No. 1 were allowed to wear to the same extent as the bits used in drilling well No. 2. This result was obtained despite the fact that in drilling Well No. 2 a greater total depth interval was obtained and the bits were employed for substantially longer periods than those used in well No. 1. Accordingly, when employing the drilling muds of my invention, the limiting factor of bit life is not the Table I Depth Inter- Drilling Adding Bit Tptal Percent Time Number of Bits Required val, Ft. Footage Time, Joints, Changes, Time, Drilling Hrs. Hrs. Hrs. Hrs.

8, 320-8, 468 148 6. 92 0. 73 5 08 12. 73 54 8, 468-8, 635 167 5. 40 0. 5 42 11. 52 46. 8 8, 6358, 849 214 8. 21 0. 97 4 37 13. 55 60. 5 Av. 54.5 8, 849-9, 020 171 6. 92 O. 62 5 32 12. 86 58. 8 9, 020-9, 198 178 9. 00 0. 5 15. 70 57. 3

Table II Depth Inter- Drilling Adding Bit Total Percent Time val, Ft. Footage Time, Joints, Changes, Time, Drilling Hrs. Hrs. Hrs. Hrs.

As will be noted from the results indicated in the tables for the two wells, less drill bits were required to make a greater amount of hole when the mud of my invention was employed. Thus, for well No. l, 5 drill hits were consumed to obtain 878 feet of hole, whereas in well No. 2, only 4 drill bits were consumed while making 1073 feet of hole. Relating the above figures to the feet per bit obtained, in well No. 2 using the mud of my invention there were obtained about 268 feet per hit, as compared with only 175.6 feet per bit in well No. 1. Expressed percentage wise, the increase in bit life thus obtained over the normal, as measured by the increased amount of hole made, was 53 percent. The above data clearly show the prolongation of bit life obtained in the practice of my invention.

The above tables also show that, while the actual drilling time expressed in percent varied with each bit employed, there was consistently obtained an increased percentage of time employed in actual drilling operations when using the mud of my invention, as compared with the mud employed in well No. 1. It is to be noted that the above tests were made under substantially identical conditions of drilling, employing the same dn'lling'rig and drilling crew and taking into consideration speed of rotation and the load on the bit.

The actual feet of hole made per hour of total drilling rig time was substantially the same, about 13 feet per hour, in both tests. This result was obtained because, in order to expose the bit bearings to the most severe test conditions when employing the drilling muds of my inbearings, as in the past, but the cutting teeth of the bit. The use of the drilling muds of my invention therefore confers the additional advantage of imparting a safety factor in drilling operations, because a bearing failure may not be expected until .after the teeth of the bit have been substantially worn out. Since bit changes will be accomplished because of tooth wear prior to the bearings approaching a dangerous condition of wear, the likelihood of cone-fishing jobs is substantially reduced.

Portions of the data of Tables I and II are shown in the attached drawings, wherein Figure 1 is a graphic representation of footage drilled versus the number of bits used, and Figure 2 is a graphic representation of the number of hours drilled with each bit in relation to the footage drilled. Figure 1 shows the increased footage per bit obtained with the muds of this invention and the increased total footage obtained notwithstanding the use of fewer bits. Figure 2 shows the prolongation of bit life in hours as well as the increased footage obtained with the muds of this invention.

There are set forth in Table III, below, numerous examples of drilling muds made in accordance with the invention. The table also includes for purposes of comparison muds which were not madein accordance with the invention. All of the muds of the examples were prepared by the following general procedure. The oil and sulfurized organic compound were mixed and the asphalt material and emulsifying agent were also added to the oil when employed. The mixture was heated to F. and stirred for 15 minutes to obtain a uniform web-e6 11 blend of the various constituents. The oily mixture was then added to a suspension of 6 percent by weight of bentonite in water, and the entire mixture was heated in an open vessel at 140 F. with sufiicient stirring to insure 12 catalyst. The sulfurized tall oil had a sulfur content of 11.6 percent by weight. The nonylphenol sulfide, the sulfurized sperm oil, and the sulfurized turpentine 'had sulfur contents, respectively, of about 10. 7, 12 and 35 complete emulsification. Prior to testing in the Timken 5 percent by weight; all of these are commercially available machine, the oil-in-water emulsion muds thus prepared products. were placed in a sealed container and aged overnight. Under the heading Oil in the table, the Naphthenic Under the Asphalt column in Table III, there ar Extract No. 1 was the oily material obtained as the shown among other asphalts Granular Petroleum extract fraction in the solvent extraction of a 400 Texas A h lw d Asphalt E t t, Th granular petroleum 10 lubricating oil distillate with furfural. The extract had asphalt employed had a melting point of 325 to 335 F. a g y f API and a Viscosity of 1170 and penetrations of 0 at 77 F. and 2 to 3 at 115 F., at 100 F. The diesel fuel oil employed had a gravity both penetrations being measured under loads of 100 f a u 11 ash POIIH of ut 173 F. and 21. grams after 5 seconds. The asphalt entitled Asphalt boillng range of ab1lt440 Extract is obtained as the asphaltic extract in the Duo- Under the heading Emulslfying Agent, the Ma-. sol solvent refining treatment of a long petroleum resi- E A6168 p y were a 46 Percent y Weight duum having a flash point of from about 450 to 500 concentrate in a lubricating oil fraction of the preferen- F. The Duosol solvents are propane and a mixture of tially oil-soluble petroleum sulfonic acids obtained as a phenol and cresylic a id The extract had an API by-product in the refining of lubricating oil fractions with gravity of 7.5 a flash point of 525 F. and a neutraliza- Oleum- The Petwnate p y was all i colleen tion number of 0.6. trate containing about 60 percent by weight of the sodium The sulfurized diisobutylene and sulfurized heptene rna- Salts f g y acids, Said Sodium Salts having terials under the heading sulfurized Organic Cornaverage 1110160111? Weight of from abmlt 445 10 pound in the table were prepared by heating to a tem- In Example 34, instead of employing bmltonite as a perature of about 300 to 350 F. diisobutylene and hepclay, a native clay from a well site was used, the contenes, respectively, with powdered sulfur for a period centration of the clay in its suspension in water being of 8 hours. In each instance, the product was steamed vl2 percent by weight. In Example 36, the clay emto strip off unreaeted hydrocarbons until a flash point ployed was a calcium base-exchanged bentonite in a conof 2607 F. was obtained. The sulfurized diisobutyleue centration of 6 percent by weight of its suspension in bad a sulfur content Of about percent Weight and water In preparing the calcium base exchanged hen. the sulfurized heptene had a sulfur content of about 50 mite, a 2 percent by weight suspension of bentonite, in percentdbg ir sulfiunzed 5:8? g 1 water was treated with lime in the proportion of 2 pounds s figi f gi fi g g g g O per barrel, well agitated and aged overnight. There- 5 re an grams 0 after, an additional amount of dry bentonite was added, powdered tron as a cataiyst. The mixture was gradually sufiicipnt t iv total b to o t {0 th heated with stirring to 320 F. and maintained at that V 0 g e a en 3 c i if n e temperature for 1% hours. After cooling and standing Suspenslon o 6 Rercent by Welght' m h addmon overnight, the sulfurized liquid product obtained was defl dry bentonite" there occurred a P Increase canted and found to contain about 5.8 percent of sulfur 40 vfsFoslty of The mud was thmned by the by Weight. The sulfurized tail oil was prepared in an dmon of calcwm hgnosulfonate in the proportion of essentially simiiar manner, omitting the use of the iron /2 pound per barrel.

Table III Asphalt sulfurized Organic Compound Oil i Emulsiiyiug Agent Tinlken Percent Total 011 Load- Example Percent Percent by Wt. Phase, Carrying Type by Wt. Type by Wt of Sulfur Type Percent Type Lb./Bbl. Capacity of Oil of Oil in Oil By Vol of Mud (Pounds) Phase Phase Phase of Drillmg Mud 2 Granular 20 sulfurized 10 4 Diesel Fuel 10 Petronate 3 65' Petroleum Diisobutyi- Oil.

Asphalt. one. 7 0 d 10 10 a 35 0 o 10 do 3 5 0 ed 10 10 Sodium Soaps 4 55 Diisobutyl- Tall Oil cne. 6 0 0 15 do 7 5 7 Granular 2 0 sulfurized 10 10 Petronate .3 30

Petroleum Diisobutyl- Extract N o. Asphalt. one. 1. s 0 10 4 10 3 o 0 0 3 1o Granular 20 sulfurized 10 4 0.75 S0 Petroleum Diisobutyl- Asphalt.

1 4 5 1.5 4 5 3 55 4 20 a so 4 40 a 100 1 10 a 2 10 3 s0 4 10 3 so 6 r0 3 s5 8 10 a p 4 10 3 s5 4 10 3 7o 4 10 3 so do 4 d0 l0 4 Asphalt Extract. 4 Diesel Fuel Oil.. 10 0 25 Granular Petro- 4 NaphthcuicExl0 Petronate 3 55' learn Asphalt. tract No. 1.

Asphalt Sulfurized Organic Compound Oil Emulsifying Agent Timken Percent Total 011 Load- Example Percent Percent by Wt. Phase, Carrying Type by Wt Type by Wt. of Sulfur Type Percent Type Lb./Bbl. Capacity of Oil of Oil in Oil By Vol. of Mud (Pounds) Phase Phase Phase of Drilling Mud do 10 4 d l0 3 15 do 10 4 Diesel Fuel Oil 10 3 60 1O 4 10 .d 3 20 d0 4 d0 10 10 3 5 20 Sulfurized Hep- 10 6 Naphthenic Ex- 10 Sorbitan Mono- 2 100 tene. tract No. 1. eate. 20 Sulfurlzed Ku- 50 2. 9 do 10 Petronate 3 85 Kalil: Crude 1 20 Nonylphenol 10 1 Diesel Fuel 011-- 3 70 Sulfide. 20 Suliurized Tall 12. 5 1. 5 Naphthenic Ex- 3 65 Oil. tract No. l. 0 Sulfurized 10 1. 2 To pedE.Ven. 1.5 35

Sperm Oil. Aii ulde, 24 35 Granular Petro- 20 Sulturized Tur- 10 3. 5 Naphthenic Ex- 3 85 leum Asphalt. pentine. tract No. 1. 36 -do 40 Sulfurized Di- 10 4 do 10 Mahogany Ac- 3 100 isobutylene. ids (46% 37 Gilsom'te 20 do l0 4 do 10 3 70 38 Granular Petro- 20 do 10 4 Mid-Continent 10 3 s5 leurn Asphalt. Bright Stock. 39 Asphalt Extract 69 -do 5 2 Diesel Fuel 011-- 10 1 100 It will be noted from the above table that conventional oil-in-Water emulsion drilling muds had substantially no lubricating properties. This is shown in Examples 4, 6 and 9, wherein the load-carrying capacities of drilling muds containing between 10 and percent by volume of diesel fuel oil or Naphthenic Extract No. 1 ranged from less than 5 pounds to 10 pounds. These minds are substantially identical with oil-in-water emulsion muds commonly employed in the field. The addition of a sulfurized organic compound, in accordance with the invention, to these drilling muds immediately resulted in a substantial increase in load-carrying capacity, Example 3 showing an increase from the low value of the mud of Example 4 to 35 pounds, Example 5 showing an increase from the low value of the mud of Example 6 to 55 pounds, and Example 8 showing an increase from the 10 pounds of the mud of Example 9 to 45 pounds. The further addition of asphalt to the drilling muds of Examples 3 and 8 resulted in a still further increase in load-carrying capacity, Example 2 showing an increase to 65 pounds, and Example 7 showing an increase to 80 pounds.

Examples 7 and 10 to 14 show subsstantially identical drilling muds varying in total oil phase from about 2 to 40 percent by volume of the mud. All of these drilling muds exhibited the improved load-carrying capacities of the invention. It is noted that a higher oil concentration is desirable if a lighter drilling fluid is required.

Examples 15 to 19 show increasing concentrations of the sulfurized organic compound in the muds of the invention, the amount of sulfur in the oil phase being varied from about 1 to about 8 percent.

Examples 20 to 24 indicate that as the asphalt content of the muds of the invention is increased the load-carrying capacities are correspondingly increased. Example 24 also indicates that, depending upon the nature of the oil phase employed, as stated earlier in this specification, it is sometimes unnecessary to employ an emulsifying agent, an excellent oil-in-water emulsion mud of superior load-carrying properties being obtained without an used to obtain the desired increase in lubricating properties. Thus, comparing Examples 15 and 20, the use of the larger amount of asphalt in Example 15 requires that only 2.5 percent of sulfurized diisobutylene need be employed to obtain a load-carrying capacity of 65 pounds, as against 10 percent of sulfurized diisobutylene in Example 20 to obtain the same load-carrying capacity.

Examples 25 through 29 show the effect of alkali metal hydroxides on the drilling muds of the invention. The asterisks adjacent the values of load-carrying capacity shown in Examples 25, 26, 28 and 29 indicate that these muds have been treated with alkali metal hydroxides. For instance, compare Example 16 with Example 25. Example 16 is a mud of the invention without having been treated with caustic soda and has a load-carrying capacity of 80 pounds. As shown in Example 25, when the mud of Example 16 is treated with 0.5 pound per barrel each of caustic soda and quebracho, the load-carrying capacity is reduced to 55 pounds. Example 26 shows that when the amounts of caustic and quebracho are increased to 1 pound per barrel, the load-carrying capacity drops to 15 pounds, a value indicating no significant lubricating properties. It is to be noted that although quebracho was used in these tests to simulate the conventional caustic soda-quebracho treatment in the field, the use of quebracho alone without caustic sodawill not result in a reduction of the load-carrying capacities of the muds of the invention.

Comparing Examples 27, 28 and 29, Example 27 shows a mud of the invention substantially free of caustic soda and having a load-carrying capacity of 60 pounds. When this mud is treated with 1 pound per barrel each of caustic soda and quebracho, its load-carrying capacity drops to 5 pounds,"as shown in Example 28. Example 29 shows the similar eiiect obtained when potassium hydroxide is substituted for sodium hydroxide in the caustic-quebracho treatment.

It is significant to note in Table III that, in every instance where there is set forth a composition in accordance with the invention, the load-carrying capacity emulsifying agent.

is always in excess of 30 to 35 pounds.

This indicates The examples also show that, when an asphalt is employed, less of the sulfurized organic compound need be that the muds of my invention have desirable lubricating properties.

It is obvious from the foregoing detailed description of the invention that I have provided superior oil-in-water emulsion drilling muds of improved lubricating properties, which prolong the useful life of drill bits by substantially retarding failure of the bearings thereof. it is therefore now possible to reduce the number of round trips required for replacing drill bits, to reduce the time lost a wet metals results in the formation of a continuous film of oil phase on the surfaces of the drill bit and the bearings thereof to the virtual exclusion of water. Accordingly, only relatively small amounts of oil phase, such as are customarily used in oil-in-water emulsion drilling muds, are necessary to obtain the desired lubrication of the bearings of a drill bit in accordance with the invention. When it is considered that the main lubricating function desired of thedrilling mud is directed to the small area of metal surface which constitutes the bearings of a drill bit, it will be appreciated that substantial economies are achieved by using the oil-in-water emulsion muds of the invention, particularly since the additives conferring the desired lubricating properties need be based only on the oil phase and not on the entire mud.

As will be apparent to those skilled in the art, conventional modifying'agents can be added to my drilling muds without departing from the spirit of the invention, provided that the muds remain substantially free of alkali metal hydroxide. Thus, there can be added the usual weighting agents, viscosity modifiers, agents for reducing fluid loss, etc.

Furthermore, I can add to the muds of this invention containing the sulfurized organic compounds set forth herein other materials which have a contributing effect on the lubricating properties of the resulting muds. For example, as described and claimed in my copending application Serial No. 465,418, filed of even date herewith, sulfur-containing asphaltic materials containing at least about 1.5 percent by weight of combined sulfur are effective in conferring improved lubricating properties on oil-in-water emulsion drilling muds. Such sulfurcontaining asphaltic materials can be the asphalt constituent of the present drilling muds, as in the case of manjak in Example 30 of the present application.- However, the asphalt constituent of the present application need not be a sulfur-containing material to be effective in enhancing the properties of the sulfurized organic compound. Thus in the present application, the asphalt may have a negligible sulfur content, as in the case of the Asphalt Extract (cf. Examples 24 and 39) which contains only0.72 percent of sulfur by Weight and gilsonite (cf. Example 35) which contains only 0.2 percent of sulfur by weight, both of which are ineffective in themselves as a sulfur-containing asphaltic material in conferring lubricating properties 'on oil-in-water emulsion drilling muds.

There is also described and claimed in my 'copending application Serial No. 465,419, filed on even date herewith, certain water-insoluble, preferentially oil-wettable inorganic sulfides which are effective in conferring lubricating properties on oil-in-water emulsion drilling muds.

I can add to or substitute for part of the sulfurized organic compounds of the present invention the sulfurcontaining asphaltic materials or the inorganic sulfides of the above copending applications, or mixtures of these is a materials, as may be dictated by considerations of cost and availability.

Resort may be had to such other modifications and variations as fall Within the spirit of the invention and the scope of the appended claims.

I claim: 7

1. A drilling mud of enhanced lubricating properties comprising an oil-in-water emulsion containing clay solids and a water-insoluble, oil-soluble sulfurized organic compound, said sulfurized compound being present 'in an amount sufficient to increase the Timken load-carrying capacity of the mud to at least about 30 pounds, said mud 7 containing no amount of alkali metal hydroxide'suflicient to destroy the enhanced lubricating properties of the mud."

2. The drilling mud of claim 1, wherein the sulfurized organic compound is selected from the class consisting of sulfurized unsaturated higher fatty acidsand their esters, 1

sulfurized open-chain olefins and polymers thereof, 'sulfurized higher molecular weight paraffinic hydrocarbons,

sulfurized crude petroleum and residual fractions there-- V i of, sulfurized terpenes, and sulfurized phenols and salts thereof. V

3. The drilling mud of claim 1, wherein said sulfurized compound is present in an amount sufficient to provide at least about 0.5 percent of sulfur by weight of the oil phase.

4. The drilling mud of compound is present in van amount suflicient to provide from about 1 to 4 percent of sulfur by weight of the oil phase.

5. A drilling mud of enhanced lubricating properties comprising an oil-in-water emulsion containing clay solids,

a water-insoluble, oil-soluble sulfurized organic compound,

said sulfurized compound being present in an amount" sufiicient to increase the Timken load-carrying capacity of the mud to at least about 30 pounds, and an emulsify ing agent selected from the group consisting of preferentially oil-soluble alkylaryl sulfonic acids and metal salts thereof, the sodium soaps of tall oil, and the higher fatty 1 acid esters of the anhydroalkitols, the amount of emulsifying agent being sufficient to reduce the surface tension of the filtrate substantially below that-of water, said mud containing no amount of alkali metal hydroxide sufiicient to destroy the enhanced lubricating properties of the mud.

6. The drilling mud of claim 5, wherein the emulsifying agent comprises the sodium salts of mahogany acids. 7. The drilling mud of claim 5, wherein the emulsify ing agent comprises sorbitan monooleate.

8. The drilling mud of claim 5, wherein the emulsifyf ing agent comprises the sodium soaps of tall oil.

I 9. The drilling mud of claim 5, wherein the emulsify ing agent comprises mahogany acids. I 10. The drilling mud of claim 5, wherein said sulfurized compound is present in an amount sufiicient to provide at least about 0.5 percent of sulfur byvweight of the oil phase. t

11. A drilling mud of enhanced lubricating propei ties comprising an oil-in-water emulsion containing clay solids, a water-insoluble, oil-soluble sulfurized organic compound, said sulfurized compound being present in an amount sufficient to increase the Timken load-carrying capacity of the mud to at least about 30 pounds, and an asphalt, said mud containing no amount of alkali metal hydroxide sufficient to destroy the enhanced lubricating 7 properties of the mud.

open-chain olefins and polymers thereof, sulfurized higher '7 molecular weight paraffinic hydrocarbons, sulfurized crude petroleum and residual fractions thereof, sulfurized tel penes, and sulfurized phenols and salts thereof, and is claim 1, wherein said sulfurized;

- 17 present in an amount sufficient to provide at least about 0.5 percent of sulfur by weight of the oil phase.

13. The drilling mud of claim 11, wherein the sulfurized organic compound is a sulfurized open-chain olefin.

14. The drilling mud of claim 11, wherein the sulfur ized organic compound is a sulfurized unsaturated higher fatty acid.

15. The drilling mud of claim 11, wherein the sulfur ized organic compound is a sulfurized ester of an unsaturated higher fatty acid.

16. The drilling mud of claim 11, wherein the sulfur ized organic compound is a sulfurized terpene.

17. The drilling mud of claim 11, wherein the amount of asphalt is from 15 to 35 percent by weight.

18. A drilling mud of enhanced lubricating properties comprising an oil-in-water emulsion containing clay solids, a water-insoluble, oil-soluble sulfurized organic compound, said sulfurized compound being present in an amount suflicient to provide at least about 0.5 percent of sulfur by weight of the oil phase, from to 75 percent of an asphalt by weight of the oil phase, and an emulsifying agent selected from the group consisting of preferentially oil-soluble alkylaryl sulfonic acids and metal salts thereof, the sodium soaps of tall oil, and the higher fatty acid esters of the anhydroalkitols, the amount of emulsifying agent being sulficient to reduce the surface tension of the filtrate substantially below that of water, said mud containing no amount of alkali metal hydroxide sufiicient to destroy the enhanced lubrication properties of the mud.

19. The drilling mud of claim 18, wherein the sulfurized organic compound is sulfurized diisobutylene.

20. The drilling mud of claim 18, wherein the sulfurized organic compound is sulfurized heptene.

21. The drilling mud of claim 18, wherein the sulfurized organic compound is sulfurized sperm oil.

22. The drilling mud of claim 18, wherein the sulfurized organic compound is sulfurized turpentine.

23. The drilling mud of claim 18, wherein the sulfurized organic compound is sulfurized tall oil. 7

24. A drilling mud of enhanced lubricating properties comprising an emulsion of a gas oil in water, said emulsion also containing clay solids, an amount of sulfurized diisobutylene suflicient to provide from about 1 to 4 percent of sulfur by weight of the oil phase, and from about to 35 percent of a petroleum asphalt by weight of the oil phase, said mud containing no amount of alkali metal hydroxide sufficient to destroy the enhanced lubricating properties of the mud.

25. A drilling mud of enhanced lubricating properties comprising an emulsion in water of an extract fraction of a solvent refined lubricating oil distillate, said emulsion also containing clay solids, an amount of sulfurized diisobutylene suflicient to provide from about 1 to 4 percent of sulfur by Weight of the oil phase, and from about 15 to 35 percent of a petroleum asphalt by weight of the oil phase, said mud containing no amount of alkali metal hydroxide suflicient to destroy the enhanced lubricating properties of the mud.

26. The drilling mud of claim additionally containing the sodium salts of mahogany acids.

27. A drilling mud of enhanced lubrication properties comprising an emulsion of a gas oil in water, said emulsion containing clay solids, an amount of sulfurized heptene sufiicient to provide from about 1 to 4 percent of sulfur by weight of the oil phase, and from about 5 to 75 percent of the asphaltic extract of a long residuum, said mud containing no amount of alkali metal hydroxide sufiicient to destroy the enhanced lubricating properties of the mud.

28. The drilling mud of claim 27 additionally containing the sodium salts of mahogany acids.

29. A drilling mud of enhanced lubrication properties comprising an emulsion in water of an extract fraction of a solvent refined lubricating oil distillate, said emulsion also containing clay solids, an amount of sulfurized heptene suflicient to provide 1 to 4 percent of sulfur by weight of the oil phase, and an asphaltite, said mud containing no amount of alkali metal hydroxide sufficient to destroy the enhanced lubricating properties of the mud.

30. A uniform blend of oily materials, usefulas' the oil phase of an oil-in-water emulsion drilling mud of enhanced lubricating properties, comprising an oil, a waterinsoluble, oil-soluble'sulfurized organic compound in an amount sufficient to provide from about 0.5 to 8 percent of sulfur by weight, and from 5 to 75 percent of an asphalt by weight, said blend containing no amount of alkali metal hydroxide suflicient to destroy the enhanced lubricating properties of the mud.'

31. The blend of claim 30, containing additionally an yemulsifying agent selected from the group consisting of V preferentially oil-soluble alkylaryl sulfonic acids and metal salts thereof, the sodium soaps of tall oil, and the higher fatty acid esters of the anhydroalkitols.

32. A process for enhancing the lubricating properties of a drilling fluid during the drilling of a well, drilling of said well having been begun with a water-base drilling mud, which comprises adding to said water-base drilling mud in the drilling fluid system of said well, an oil and a Water-insoluble, oil-soluble sulfurized organic compound in amounts effective to convert said Water-base drilling mud to an oil-in-water emulsion drilling mud having a Timken load-carrying capacity of at least about 30 pounds,

said mud containing no amount of alkali metal hydroxide sufficient to destroy the enhanced lubricating properties of the mud, circulating the resulting mixture through said drilling mud system, and continuing drilling of the well.

33. The process of claim 32, wherein the amount of said sulfurized organic compound is sulficient to provide at least about 0.5 percent sulfur by weight of the oil phase.

34. The process of claim 32, wherein there is also added to the water-base drilling mud an asphalt blended with the oil.

37. A process of drilling a well with a rotary bit which comprises forming a borehole with said bit while circulating a drilling mud of enhanced lubricating properties through said borehole, said drilling mud comprising an oil-in-water emulsion containing clay solids and a waterinsoluble, oil-soluble sulfurized organic compound, said sulfurized compound being present in an amount sufficient to increase the Timken load-carrying capacity of the mud to at least about 30 pounds, said mud containing no amount of alkali metal hydroxide suflicient to destroy the enhanced lubricating properties of the mud, whereby the life of the bit is prolonged.

38. A: uniform blend of oily materials, useful in the oil phase of an oil-in-water emulsion drilling mud of enhanced lubricating properties, comprising an oil, a Water-' asphalt and an emulsifying agent selected from the group consisting of preferentially oil-soluble alkylaryl sulfonic acids and metal salts thereof, the sodium soaps of tall oil,"

and the higher fatty acid esters of the anhydroalkitols,

said blend containing no amount of alkali metal hydroxide suflicient to destroy the enhanced lubricating properties of the mud.

(References on following page) References Cited in the' file of this patent UNITED STATES. PATENTS Kaufman June 1956 Lubricants, article in Scientific Lubrication; Sept. 1950; G July 13 1947 5 pages 7, 8, 11- and14. V r i 195-1 Rogers: Composition and Properties of Oil Well Drill- $13 2; 23x 3 ing Fluids, revised edition, pub. 1953 by Gulf Pub. Co?

OTHER REFERENCES on, Nov. 1950, Drilling Section, pages 101, 102, 103; 104

and 106.

Davey: The Mechanism of Action of Extreme Pressure of Houston, Texas,- pages 511, 513 and 51ft. V 

1. A DRILLING MUD OF ENHANCED LUBRICATING PROPERTIES COMPRISING AN OIL-IN-WATER EMULSION CONTAINING CLAY SOLIDS AND A WATER-INSOLUBLE, OIL-SOLUBLE SULFURIZED ORGANIC COMPOUND, SAID SULFURIZED COMPOUND BEING PRESENT IN AN AMOUNT SUFFICIENT TO INCREASE THE TIMKEN LOAD-CARRYING CAPACITY OF THE MUD TO AT LEAST ABOUT 30 POUNDS, SAID MUD CONTAINING NO AMOUNT OF ALKALI METAL HYDROXIDE SUFFICIENT TO DESTROY THE ENHANCED LUBRICATING PROPERTIES OF THE MUD. 